1. Field of Invention
The present invention relates to a control circuit, and more particularly to a charge pump circuit which is capable of automatically adjusting the charge and discharge current based on the impulse width of the signal.
2. Description of Related Arts
The phase separation between the output signal and the input signal of the phase-locked loop (PLL) and delay-locked loop (DLL) is needed to be identified by the phase frequency detector. The phase separation is integrated by the charge pump such that the integral result is embodied in the control voltage in the form of the voltage variation. The control voltage is used to control the voltage control oscillator or voltage-controlled delay line till the phase synchronization between the two signals is achieved. In generally, the conventional charge pump circuit only has a branch of working current, so that the locking time of the phase locked loop is limited.